It is general knowledge to use balanced amplifiers in radio stations for amplifying a transmitter signal in order to improve efficiency. A balanced amplifier comprises a first amplifying device and a second amplifying device that are operated in parallel. A quadrature splitter at an input of the balanced amplifier phase shifts an input signal of the balanced amplifier to a first signal portion and a second signal portion which are 90 degrees apart in phase. The first signal portion is amplified by the first amplifier device and the second signal portion is amplified by the second amplifier device. The first amplified signal portion and the second amplified signal portion are re-combined in a quadrature coupler which shifts the phases of the first amplified signal portion and the second amplified signal portion such that the first amplified signal portion and the second amplified signal portion are combined in phase. Such balanced amplifiers are more immune to load pull effects than in-phase power combining schemes, because any reflected signals are 180 degrees apart in phase and thus substantially cancel each other when combined.
The use of mobile communications networks has increased over the last decade. Operators of the mobile communications networks have increased the number of base stations in order to meet an increased demand for service by users of the mobile communications network. The operators of the mobile communications network wish to purchase components for the base stations at a lower price and also wish to reduce the running costs of the base station. Since power amplifiers consume more than 50% of the total power of a transmitter system improvements in the efficiency of the power amplifier technology are the most promising contributors to more efficient base transceiver stations and/or active antenna arrays.